A texture is an image or other sampled field used to vary a surface property across geometry.

Vertices can carry texture coordinates, commonly written $(u,v)$, that identify locations in a 2D texture domain. During rasterization these coordinates are interpolated across the triangle, then used to sample the texture for each fragment.

Texture coordinates are independent of the model's spatial coordinates. The same image can be mapped onto different shapes, and one mesh can use different parameterizations without changing its 3D positions.

A texture can provide more than visible color. The sampled values may represent roughness, opacity, surface-normal perturbations or arbitrary material parameters.

Mapping a 2D domain onto a 3D surface introduces seams and distortion unless the surface has a naturally compatible parameterization. Texture coordinates therefore encode a deliberate correspondence between surface locations and sampled data.

Under perspective projection, texture coordinates must be interpolated with the same perspective correction as other projective vertex attributes.